Various techniques such as a technique using a reference light to measure the intensity or return time of a light reflected from a subject, or a stereo ranging technique using a plurality of cameras are known as imaging techniques for obtaining two-dimensional information on the depth-direction distance to a subject. Use of such image information for obtaining a distance (hereinafter also referred to as the “distance image information”) enables subject recognition that is more sophisticated than subject recognition based on image information obtained from regular cameras. Devices that can obtain distance image information are therefore increasingly needed as relatively inexpensive products used as consumer appliances, games, and industrial devices.
With imaging techniques for obtaining distance image information, a compound-eye imaging device having an imaging lens and capable of obtaining a large number of parallax images and measuring a distance based on triangulation with a single camera is proposed. Such an imaging device includes, for example, a main imaging lens, and a plurality of optical systems serving as re-imaging optical systems between the main imaging lens and an imaging element. An example of the aforementioned optical systems is a micro lens array having microlenses on a plane surface. Pixels are arranged under the microlenses at locations corresponding to the respective microlenses in order to obtain images formed thereby. An image formed by the main imaging lens is re-imaged on the imaging element by the re-imaging microlenses with viewpoints being shifted due to parallaxes existing at the locations of the respective microlenses (parallax image group). The distance to the subject can be estimated based on the principles of triangulation by performing image processing on the parallax image group obtained from the microlenses. Furthermore, a two-dimensional image can be reconstructed from the images by performing image processing to combine the images.